Published annually The Post Office Annual Directory and Calendar for Dublin is an extremely rare and valuable source of information for anyone researching ancestors from Dublin. First published before Thom's Directories it provides information for a time when very few other sources of information still exist.

This edition, from 1858, has over 700 pages and a wealth of information.

Like many other directories The Post Office Directory has listings of all the government, military, religious, educational, medical, legal and police establishments both in the city and county. There is a also a listing of the gentry and peerage of Ireland.

The majority of the directory is taken up with lists of the nobility, gentry, merchants and traders of the city and surrounding vicinity. This is followed by listings for many of the professions, such as the legal and medical professions. There is also an alphabetical list of the streets and lanes of the city itself, but unlike the 1843 directory this edition does contains the names of residents and businesses at each address.

Also included in this directory is considerable information of 53 suburban towns and villages. In the case of the larger suburban areas like Bray and Kingstown street directories, including the residents, are also covered.The remainder of the directory is taken up with the Post Office section of the directory, giving listings of the post towns, postage rates, as well as details of the mail and stage coaches from Dublin.